Since you're taking asks for the AU, how did characters end up part dragon? Did they have a parent or ancestor who transformed to pass as human?
Yes! Like Suiryu and Suiko are doing, all dragons can shapeshift into humans (and other animals if they felt like it, but there's rarely a reason to). Most of them would tell their human partner long before having a child with them, but there are always assholes and accidents.
Mumen's great-great-grandfather was married to his great-great-grandmother but left the family after she passed away. Genos doesn't remember but he actually had two moms and they were married too.
(I haven't managed to work it into a comic yet but dragons can change their biological sex like some fish and frogs. Suiryu would have to spend about six months controlling his temperature before he can lay eggs, but if you find a good sire it's worth it.)
